Go Nagai's original manga is frequently archived in various languages. Additionally, you may find scans of vintage magazines from the 1970s and 80s (such as TV Magazine or Shonen Jump ) featuring original artwork and articles about the series when it was first airing.
The Archive holds PDFs of out-of-print mook (magazine/book hybrids) from the 90s, such as the Mazinger Z Great Encyclopedia . These books contain mechanical schematics of the Hover Pilder, cross-sections of the God Scrander, and interviews with Go Nagai. A physical copy of these books can cost $200+ on eBay. On the Archive? Freely downloadable. Mazinger Z Internet Archive
Not everything on the is high quality. These are fan uploads. You will find: Go Nagai's original manga is frequently archived in